NGF and Alzheimer disease: Studies in transgenic animal models of AD indicate that the proinflammatory process—initiated before plaque deposition and promoted by soluble Aβ oligomers—leads to an impairment of NGF metabolic pathway characterized by a reduced conversion of the precursor proNGF to the mature NGF (mNGF) as well as by an increased deprivation of mNGF (18, 132, 134).